“Double block and bleed” is a well-known term of art that refers to setting two seals in a pipe and opening a bleed port between the seals to ensure that the first seal is holding. Any leakage past the first seal is contained by the second seal and forced to exit through the bleed port. This arrangement ensures that the pipe is completely sealed, making it safe to work on downstream of the two seals.
Achieving double-block and bleed, however, currently requires the use of a single, metal-to-metal plugging seal or the use of two independent pluggers and fittings. Both approaches are expensive; use relatively large, heavy components; and require a lot of equipment to properly install. Additionally, the metal-to-metal plugging seal approach does not allow for bypassing pipeline product through a fitting. If a bypass is required, a second fitting must be installed upstream of the plugging seal. Therefore, a need exists for a double block and bleed plug that is less expensive, smaller and lighter weight, and easier to install than the current approaches. None of the prior art alone or in combination meets this need or renders the present invention obvious.
For additional information relating to pipe pluggers, reference may be had to the following previously issued United States patents.
Patent NumberInventorTitle386,446BaileyApparatus For Detecting Leaks In Soil and Other Pipes411,978ChisholmPipe Stopper1,181,984ArniTest Plug1,221,733HendersonTest Plug2,279,257SvirskyExpansible Closure Means For Conduits2,812,778Ver NooyPipe Line Plugger2,886,068Ver NooyPipe Line Plugger2,906,295Ver NooyPipe Line Plugger3,154,106Ver NooyPipeline Plugger3,442,294Bischoff et al.Closure Means For Use During Pressure Testing Of Pipes or The Like3,665,966Ver NooyPipe Plugger3,774,646SmithLine Stopping Assembly Using An Inflatable Element3,774,647Saha et al.Line Stopping Assembly Using An Inflatable Element3,902,528Tartabini et al.Pneumatic Plug For Hydraulic Conduits4,040,450BoundyPipe Sealing Apparatus4,064,912PetroneGas Main Stopper4,202,377HarrisonPipe Cleaning and Plugging Apparatus4,505,295Quin et al.Apparatus For Inserting A Shut-Off Device Laterally Into A Pipe4,682,631Wilger et al.Sealing Apparatus For A Valve Body Opening5,029,614Lara et al.Tandem Seal System For Testing Pipelines5,082,026SmithPipeline Plugger5,297,581GodfreyPipeline Plugger5,844,127Berube et al.Apparatus For Isolating or Testing A Pipe Segment6,062,262TashWater Drain Pipe Test Plug Device6,289,935TashDrainpipe Test Plug Device6,601,437GotowikApparatus For Testing or Isolating A Segment Of Pipe6,659,133RussellInsertable Line Stopper Plug For Pipelines7,240,697Beebe et al.Apparatus and Method For Isolating and Testing A Segment Of Pipelines7,270,139Calkins et al.Cam-Assisted, Wedge Actuated, Metal-to-Metal Seal, Block and BleedPlugging Tool7,281,543Calkins et al.Apparatus, Systems and Methods for Plugging a High Temperature Pipe2007/0018452LeePipe Interruption FittingEP 0488966 A1RavettiStopper Device For Gas Tubes